|Authors||Essig G, Porter K, Schneider DF, Arpaia D, Lindsey SC, Busonero G, Fineberg D, Fruci B, Boelaert K, Smit J, Meijer J, Duntas LH, Sharma N, Costante G, Filetti S, Sippel RS, Biondi B, Topliss DJ, Pacini F, Maciel RM, Walz P, Kloos RT|
|Publish Date||2016 Sep 7|
Current surgical standard of care in sporadic medullary thyroid carcinoma (sMTC) consists of a minimum of total thyroidectomy with central neck dissection. Some have suggested thyroid lobectomy with isthmusectomy and central neck dissection for patients with sMTC given their lower frequency of bilateral disease, although this topic has not been thoroughly studied. We assessed the prevalence of multifocality in sMTC via a large international multi-institutional retrospective review to quantify this prevalence, including the impact of geography, to more accurately assess risks associated with alternative surgical approaches.A retrospective chart review of sMTC patients from 11 institutions over 29 years (1983 to 2011) was undertaken. Data regarding focality, extent of disease, RET germline analysis plus family and clinical history for multiple endocrine neoplasia type 2 (MEN2), and demographic data were collected and analyzed.Patients from 4 continents and 7 countries were included in the sample. Data for 313 patients with documented sMTC were collected. Of these, 81.2% were confirmed with negative RET germline testing while the remaining 18.8% demonstrated a negative family history and no manifestations of MEN2 syndromes other than MTC. Bilateral disease was identified in 17/306 (5.6%) of patients, while multifocal disease was noted in 50/312 (16.0%) of sMTC patients. When only accounting for germline negative patients, these rates were not significantly different (5.6% and 17%, respectively). Among them, when disease was unifocal in the ipsilateral lobe and isthmus, bilateral disease was present in 6/212 (2.8%) of cases. When disease was multifocal in the ipsilateral lobe or isthmus, then bilateral disease was present in 8/37 (21.6%) of cases (p<0.001 by Fisher’s Exact Test). No geographic differences in focality were identified.The 5.6% prevalence of bilateral foci in sMTC suggests that total thyroidectomy should remain the standard of care for initial surgery as less complete thyroid surgery may fail to fully address the primary site of disease. Whether ipsilateral tumor focality should be an independent factor determining the need for completion thyroidectomy when sMTC is diagnosed after hemithyroidectomy remains to be determined.